The prior art teaches various methods and systems for determining when it is required to change the oil in the engine of an automotive vehicle. These systems normally include an in-vehicle display activated by the operator, which signifies the current status of the oil. Vajgart et al., in U.S. Pat. No. 5,060,156, discloses a system for determining oil change intervals as a function of the number of engine revolutions. The number of engine revolutions are weighted as a function of oil temperature. Imajo et al., in U.S. Pat. No. 4,706,193, discloses an oil degradation warning system in which the oil degradation is computed as an integrated function of oil temperature, distance driven and engine speed, while Inoue, in U.S. Pat. No. 4,796,204, discloses an oil degradation warning system which generates three different degradation coefficients. Each of these degradation coefficients are an integrated function of oil temperature, engine speed and engine load weighted differently. Inoue further teaches a warning to change oil is provided when any one of the three degradation coefficients exceeds an associated limit. Korb, in U.S. Pat. No. 4,845,623, discloses an oil change warning system in which the actual number of miles remaining before oil change is displayed. The distance being traveled is weighted by oil temperature and engine speed. Finally, Moon, Sr., in U.S. Pat. No. 4,884,054, teaches a self-contained system which issues a warning to change the oil as a function of time.
The prior art has taught that the monitoring of the status of the oil in the engine is considered to be of significant importance and that systems which monitor the oil status and provide warnings to the vehicle's operator when it is time to change oil will be available in all automotive vehicles in the near future.